The floating UFO

Again, Ernie’s Gang was up to no good.

“Aliens! The aliens are coming!”

Ernie and his friends were at a stand selling pictures.

Jack walked over and calmly asked “What’s going on?”

Ernie told them: “You know that military base in Southampton?

“Yeah?”

“I have an uncle who works there, and they’ve spotted some UFOs in the past. My uncle gave me some of their photos and look!”

He held up a dark photo with a shining green hovering sphere watermarked 8:30.

“Is that 8:30 in the morning or in the afternoon?” Jack asked.

“What do you think this is? Morning? Nah, it’s 8:30 in the night. Want to buy one for £20?” Elton replied.

“For a fake photo?” asked Jack.

How did Jack know?